A PWM driver attempts to maintain a desired current level through a load by modulating the duty cycle of a direct current (DC) source being switched at a designated frequency. A PWM driver controller selectively supplies low amperage trigger signals to a switched power circuit, for example to the gate of a N-channel MOSFET transistor electrically connected in series with the load and DC source, such as a battery (BATT). A sensed value representative of the current flowing through the load is in turn fed back to the controller, in order to enable the switch to be turned off when the current is above the desired level and turned on when below the desired level.
It is generally desirable to enable the target current to be variably selected under the control of a programmed microprocessor. For example, the microprocessor may supply the PWM driver controller with a target current control signal, having a duty cycle representative of the desired load current, and a switching frequency control signal having a duty cycle representative of the desired frequency. Such an arrangement however, ties up two serial data lines of the microprocessor for each PWM driver utilized. Even when it is possible for multiple PWM drivers to share the same switching frequency control signal, continuously generating the appropriate control signals requires additional program code and some substantial portion of the time available to the microprocessor needed for overall system control.
Likewise it is undesirable for the microprocessor to monitor the pulse width modulation driver substantially continuously in order to detect electrical faults in the load circuit and prevent damage.
The present invention is directed to overcoming one or more of the disadvantages set forth above.